Electric annealing apparatus



July 19, 1932. E. A. COLBY ELECTRIC ANNEALING APPARATUS 4 Sheets-Sheet IFiled Oct. 21, 1950 y 1932- E. A. COLBY ELECTRIC ANNEALING APPARATUSFiled Oct. 21. 1950 4 Sheets-Sheet 2 ATTORNEYfi July 19, COLBY ELECTRICANNEALING APPARATUS Filed Oct. 21, 1930 4 Sheets-Sheet 5 ATTORNEYS July19, 1932. A, L Y 1,867,810

ELECTRIC ANNEALING APPARATUS Filed 00b. 21, 1930 4 Sheets-Sheet 4ATTORN'EYS Patented July 19, 1932 UNITED STATES EDWARD A. COLBY, OFMAPLEVJOOD, NEW JERSEY, ASSIGNOR TO BAKER & COMPANY,

INC A CORPORATION OF NEW JERSEY ELECTRIC ANNEALIHG APPARATUS Applicationfiled October 21, 1930. Serial No. 490,202.

This invention relates to an apparatus for annealing metals and theiralloys in wire or strip form, and is especially applicable to metalwires or strips having a relatively small cross-section or low tensilestrength.

One important feature of the invention is an improved electric furnace.

It has been common practice for many years to anneal metal wires bycoiling them on metai spools as supports in mufiie heated furnaces.Unless the wire has an oxide or other protective coating, contactingconvolutions of the wire frequently weld together at the annealingtemperatures, thereby causing loss of labor and material. Theapplication and removal of any protective coating complicates theprocess of wire drawing, makes it difficult to secure uniform results,and is not permissible when the wire must be anno nealed at the finishedsize. The trend today appears to be toward a revival and improvement offormer experimental methods of annealing by the linear passage of wirethrough refractory tubesheated by coal or gas fuel, or

more recently by electric current. Such furnaces are usually arrangedwith their tubular channels in a horizontal or slightly inclinedpostion, and the wires are drawn through the tubes in contact with theinner so Walls of the tubes so that the hot wires often becomecontaminated from the tubes or foreign matter therein, or if sufficienttension is applied to avoid physical contact of the wires with thetubes, the cross-sectional areas of the wires are reduced by thetension.

One object of the invention is to provide a novel and improved annealingapparatus wherein the wire shall be linearly passed through a heatedtube in such a manner as to the tube and obviate such tensile strain ofthe wire as would reduce the cross-sectional area thereof. Anotherobject is to provide an electric annealing furnace for the purposedescribed including a metal tube through which the wire to be annealedmay be passed linearly, said tube itself serving as the resistor to heatthe wire passing therethrough and being mounted so as to preventbuckling, bending avoid contact of the wire with the walls of or otherdeformation of the tube as the result of expansion and contractionthereof.

Other objects of the invention are to provide an annealing apparatus ofthe character described whereby uniformity of annealing of long lengthsof wire may be obtained by variable control of both temperature and theperiod of treatment of wire thereto; to provide such an apparatuswhereby the wire may be successively annealed and drawn; to provide anelectric annealing furnace embodying novel and improved features ofconstruction whereby economy of heat transferred from the furnace to thewire being annealed is attained and external radiationreduced to aminimum; to obtain any desired speed of heating or of cooling of thefurnace and the material being annealed to facilitate manual handling ofthe furnace or the material, and to obtain other advantages and resultsas will be brought out by the follow ing description.

For the purpose of illustrating the principles of the invention I haveshown in the accompanying drawings one form of annealing apparatusembodying my invention, but it should be understood that this isprimarily for the purpose of illustrating the principles of theinvention and that many modifications and changes can be made in thedetails of construction of the apparatus without departing from thespirit or scope of the invention.

Referring to said drawings, in which corresponding and like parts aredesignated throughout the several views by the same referencecharacters,

Figure 1 is a front elevationof the annealing apparatus;

Figure 2 is a side elevation thereof;

Figure 3 is an enlarged fragmentary transverse vertical sectional viewthrough the electric furnace embodying the invention, taken on the line3-3 of Figure 1;

Figure 4 is a similar view showing the ap paratus from a position atright angles to that illustrated in Figure 3;

Figure 5 is a top plan view of the electric furnace shown in Figure l;

Figure 6 is a horizontal sectional view, on the line 6 6 of Figure 4;;

Figure 7 is a bottom plan view of the furnace;

Figure 8 is a fragmentary transverse vertical sectional View showing anattachment to the furnace for cooling the wire after annealing to atemperature below the oxidizing temperature of the particular metal ofwhich the wire is formed;

Figure 9 is a similar view showing another attachment for preventingoxidation of the wire during the annealing operation;

Figure 10 is a horizontal sectional view, on the line 1010 of Figure 1;

Figure 11 is a fragmentary top plan view of the apparatus shown inFigure 1, and

Figure 12 is a fragmentary front elevation of the apparatus showing themanner of using it in connection with a wire-drawing machine.

Specifically describing the invention, the apparatus preferably includesa portable stand or support which can be conveniently moved from placeto place wherever it is desired to anneal wire or the like, and saidstand may consist of a base 1 mounted on casters or the like 2 andhaving secured thereto four uprights or standards 3 at the top of whichis mounted a top piece 4.

Upon this stand is mounted substantially centrally between the standards3, my improved electric furnace A. This furnace is connected in thesecondary circuit of a known type of transformer B and an ammeter C, asby wires 5, 6 and 7. The circuit through the primary winding of thetransformer B is controlled by a rheostat D, the current to which fromline wires E is controlled by a cut-off switch F. As schematically shownin Figure 2 of the drawings, the secondary of the transformer isconnected to one terminal of the ammeter by a Wire 8. The trans formerB, rheostat D, switch F and ammeter C are mounted upon the stand in anysuitable manner, as shown. The constructions of these electrical devicesand the circuit connections therefor are all old and well known, and noclaim to novelty is made thereon.

The wire or the like to be annealed is wound upon a spool G which isplaced upon the base 1 of the stand centrally between the standards andsubstantially coaXia-lly with the electric furnace A, and the Wire Hpasses vertically upward through the furnace, where the wire is heatedfor annealing, and then outwardly over a guide pulley I adjustablymounted at K on the stand, from where the wire may be wound upon a drumor reel L actuated by suitable driving mechanism M from a motor or thelike enclosed in a casing N. Thewire is unwound from the spool and drawnthrough the furnace by the winding drum L.

However, it is not necessary to use the winding apparatus described, andthe wire may be passed directly from the furnace to a wire-drawingmachine, or other machine by which it may be desired to treat the wiresubsequently to the annealing operation, as hereinafter described, andaccordingly the winding apparatus L, M, N is preferably detachablymounted upon the stand as by brackets 0.

Coming now to the electric furnace A, which is the important feature ofmy invention, the furnace includes an outer wall or casing 9, which ispreferably cylindrical and tubular, formed of any suitable materialwhich is a poor conductor of both heat and electricity and hassufficient mechanical strength to serve as a support. One refractorymaterial possessing these desired characteristics is unbaked soapstone,which has the additional advantageous characteristic of being easilymachined and susceptible of being made in short sections which can bemechanically connected to provide a furnace wall of any desired length.This insulating casing 9 of the furnace may be supported upon the standin any suitable manner, as by a bracket arm 10 secured to the casing andadjustably mounted as by a set screw 11 upon one of the standards 3.

Centrally orcoaxially within the casing 9 is mounted a tube 12 whichserves as the channel through which the wire or the like to be annealedis passed. This tube also serves as the resistor for heating the wire,and is preferably formed of a seamless drawn metal tube of such length,bore, thickness of wall, and other cha acteristics as may be necessaryto satisfy requirements. If the annealing temperatures are to be notabove 1,000 C., a nichrome tube may be used, while for highertemperatures up to 1,500 0., alloys of the platinum group of metals arepreferable because they are non-oxidizing. For still higher temperaturesmolybdenum and tantalum can be used if provision is made to keep thembathed in an inert gas.

This resistor 12 is fixedly connected at one end to the upper end of thecasing 9, as by a metal can 13 which has arms to embrace the casing andclamped together by a screw 14, whereby the cap is securely mounted onthe casing. The tube preferably has a bushing 15 welded thereto, whichis in turn welded to the cap 13. Welded upon the other end of the tubeis an exteriorly threaded bushing 16 which passes through an opening ina stirrup-like member 17 and has a nut 18 for 20 secured on the casingin a groove 21 by screws 22. The bushing 16 passes loosey through anopening 23 in a refractory cyiiridrical block 24 looseiy slidable in thecasing 9 and supported upon the stirrup 17. Vi ith this construction,the tube 12 is suspended so i 5 that its weight normally tends to keepit straight, and the lower end is free to move relatively to the casing9 to compensate for expansion and contraction of the tube as it isheated and cooled, respectively, so that buckling or bending of the tubeis prevented. The block 24. serves to maintain the tube centrally of thecasing. The spring arms 19 of the stirrup also normally exert a slighttension upon the tube to aid in preventing bending or buckling thereof.The cap 13 and the collar 20 serve as terminals for connecting the tubein an electric circuit with the transformer B, and preferablyZI-ilGXlblB loop 25 formed of a good electrical conducting metal,

such as silver, is'provided for connecting the two halves of the collar20 to ensure equal diversion of current between the four spring circuitmembers 19.

The bore of the tube 12 is madeas small as possible for efficiency ofoperation, and I have found that a one-eighth inch bore is ample forfishing wire throughthe tube for annealing. It will be noted that theheat is directly transmitted from the resistor tube 12 to the wire beingannealed, so that great efiiciency in heating is obtained, and the airspace between the tube and the casing 9 reduces to a minimum the loss ofheat from the resistor externally. Any increase in the diameter of thebore above that needed for the mechanical handling of the wire to beannealed, results in a loss of efliciency in the transmission of heat tothe work, both be cause of greater space between the wire and the tubeand the greater radiating surface of the tube, and any contact of saidtube with heat conducting material would result in a loss of heat fromthe tube.

In operation of the apparatus, the wire to be annealed is drawn from thespool or drum G through a guiding eye 26 disposed below and in axialalinement with the lower end of the resistor tube 12, after which thewire is threaded through the resistor tube upwardly and over the pulleyI at the top of the stand. From this pulley the wire may be directlyconnected to a wind-up drum L, or if desired, passed directly throughwire-reducing dies P, as shown in Figure 12 of the drawing. hen it isdesired to draw the wire immediately after annealing, the stand may bemoved alongside of and connected to a wiredrawing machine Q, by asuitable bolt and nut connection R. The wire is then drawn through theresistor tube and is suspended from the pulley I so as to remainsubstantially centrally of the resistor tube and out of contacttherewith. The only tension on the section of the wire is caused by theweight of the wire, so that there is a minimum tendency toward reductionin crosssectional area of the wire while it is being annealed. Uponturning on the switch F, the desired temperature of the tube 12 may beobtained almost instantaneously by adjustment of the rheostat D, asthere is no solid body conduction of heat from the resistor except atits tenninals. This construction effects not only high efiiciency inheat transfer from the tube 12 1,

to the wire, but, upon opening of the switch F, equally rapid cooling ofthe tube results so that the fishing of new wire through the tube andhandling of the furnace is greatly facilitated.

Variations of annealing temperatures may be controlled according to therate of heat development in the resistor tube which is indicated by theammeter C, current flow, or by a thermocouple in contact with theexternal wall of the tube 12, while the time of annealing may becontrolled both by the length of the resistor tube 12 and the speed ofmovement of the wire therethrough. Absorption of heat by wire passingthrough the resistor 3 tube is practically instantaneous, so that forordinary speeds of wire drawing, wires of .025 inches are thoroughlyannealed by passage through a resistor tube of one-eighth inch bore anda length of thirteen inches when the temperature of the metal of theresistor tube is approximately 1,500 C. When it is desired to annealoxid-izable metals in this type of furnace, detachable extensions may beadded to both ends of the resistor tube. For example, when it is desiredto gradually reduce the temperature of the wire after it emerges fromthe resistor tube, so as to prevent oxidation of the wire, an extension27 is attached to the cap 13, as shown 3 in Figure 8 of the drawings.This extension may consist of a hollow casing having centrally thereof atube 28 to be alined with the resistor tube 12. In the space'270 betweenthe tube 28 and the walls of the casing may be i circulated a coolingliquid, such as water, through pipe connections 29 and 30. Such'aconstruction ensures the cooling of the annealed wire below itsoxidation point on its emergence to the outer atmosphere.

Oxidation of the wire passing through the furnace may'also be preventedby detachably connecting a block 31 to the nut 18 at the lower end ofthe resistor tube, as shown in Figure 9; said block having a centralpassage 7 32 to aline with the resistor tube 12 and through which passesthe wire, 'andalateral passage 33 communicating with the passage 32 andto be connected as by'a pipe 34to a supply of steam or dry inert gas.Upon in- 'wire,.and'some of thegas passesupwardly and outwardly throughthe resistor tube, so that thewire being annealed is bathed in the steamor gas, and oxidation of the wire thereby prevented.

It will beunderstood that while I have luv shown and described theapparatus for annealing a single wire, the diameter of the resistor tube12 can be enlarged to permit the simultaneous passage of several wirestherethrough properly guided at both the lower and upper ends; However,it is practical and economical to use separate resistor tubes for eachwire being annealed. To increase the output of the apparatus, both thelength of the resistor tube and the speed of travel of the wiretherethrough may be increased.

While I have shown and described the invention as embodied in certaindetails of construction, it should be understood that this is primarilyfor the purpose of illustrating the principles of the invention, andthat many modifications and changes may be made in the details ofconstruction, by those skilled in the art, without departing from thespirit or scope of the invention.

Having thus described the invention, what I claim is:

1. An apparatus for annealing long'continuous pieces of material,comprising a heat insulating casing, a tube of electricity-conductingmaterial suspended in insulated relation at its upper end substantiallyvertically in said casing and in spaced relation between its ends to theinner walls of said casing so as to provide a heat insulating air spacebetween the casing and said tube with the lower end of said tube freefor movement upon expansion and contraction of the tube, through whichthe material to be annealed is linearly passed, so that gravitationalaction tends to prevent buckling or bending of said tube and the tube isrelieved of all friction resistance to expansion and contraction, andmeans for connecting the opposite ends of said tube in an electriccircuit.

2. An apparatus for annealing long cintinuous pieces of material,comprising a heat insulating casing of tubular form, a tube ofelectricity conducting material suspended in insulated relation at itsupper end substantially vertically in said casing and in spaced relationbetween its ends to the inner walls of said casing withits lower endfree for movement upon expansion and contraction of the tube, throughwhich the material to be annealed is linearly passed, meanssubstantially closing said casing interposed between the lower end ofsaid tube and said casing for holding the tube in spaced relation to thein- 5 ner walls of said casing, whereby a heat insulating air space isprovided between said tube and said casing and a minimum of heatconducting contact of said tube with other parts is ensured, andgravitational action tends to prevent buckling or bending of said tubeand the tube is relieved of all frictional resistance to expansion andcontraction, and means for connecting the opposite ends of said tube inan electric circuit.

3. An apparatus for annealing long continuous pieces of material,comprising a support, a tube of electricity-conducting mate rialsuspended only at its upper end in insulated relation substantiallyvertically on said support and free throughout its length for movementupon expansion and contraction of the tube, through which tube thematerial to be annealed is linearly passed, means for connecting theopposite ends of said tube in an electric circuit, and a springconnection between said support and the lower end of said tube to exertslight tension on the tube to restrain buckling or bending thereof.

4. An apparatus for annealing long continuous pieces of material,comprising a heat and electricity insulating casing of tubular form, ametal cap at the upper end of said casing, a tube ofelectricity-conducting material suspended at its upper end on said capsubstantially centrally and vertically in said casing and in spacedrelation to the walls thereof with its lower end free for movement uponexpansion and contraction of the tube, through which tube the materialto be annealed is linearly passed, means at the lower end of said tubefor holding it centrally of said casing, means for connecting said capin an electric circuit, and a spring connection between said casing andthe lower end of said tube to exert slight tension on the tube torestrain buckling or bending thereof and for connecting said tube in anelectric circuit.

EDWARD A. COLBY.

